a. Field of the Invention
This invention relates to an ionic conductive polymer or a polymeric solid electrolyte.
b. Description of the Prior Art
There have recently been developed solid electrolytes of organic polymers which have such advantages that (1) they are easier to mold and also to make thin films of large areas and (2) they are more flexible and more excellent in adherence to electrodes than inorganic solid electrolytes.
As a polymeric solid electrolyte, M.B. Armand et al. proposed a mixture of polyethylene oxide and a salt of alkali metal salts (Fast Ion Transport in Solids, 131, 1979). However, the conductivity of the solid electrolyte is less than 10.sup.-6 S/cm at room temperature, the strength of its thin films being weak, and its adherence to electrodes is not satisfactory. Hence, its improvement has been desired.
In order to increase the film strength, there have been proposed a method of crosslinking by the reaction of a trifunctional polyethylene glycol and a diisocyanate derivative (Japanese Patent Laid-Open No. 48716/1987), a method of crosslinking to form network molecules by the polymerization of polyethylene glycol diacrylate (Japanese Patent Laid-Open No. 285954/1987), and other methods. However, further improvements have been desired in the balance of properties such as film strength, ionic conductivity and adherence to electrodes.